Guys, I need help on this one. My wife was stranded for several hours on the highway yesterday; the temp guage was in the red, and the message was about coolant temperature. When I got there to assist her, having bought two gallons of coolant, lo and behold,the plastic coolant tank was FULL. What is going on? Does this mean the water pump has gone out? All the belts seem to work, so I can't figure out what is causing the overheating. Any competent diagnosis would be appreciated.